448 



DR. C. CHREE, EXPERIMENTS ON ANEROID BAROMETERS 



I have calculated in this way from Table I., in the case of all but the shortest range, 

 the differences of the descending and ascending readings answering to the fractions 

 0, '1, '2, -3, &c., of the range, measured from the lowest point. For the range 30-24 

 inches the first group of aneroids was used. The ratios borne by these calculated 

 differences to the mean differences in Table I. are given in Table II. 



It should be noticed that the mean of the 11 differences found for the 



fractions 0, '1, &c., of the range is not generally identical with the difference cl given 

 in Table I. ; consequently the sum of the 1 1 entries in each row of Table II. is 

 not identically 11, though nearly so. .In deciding to take the d of Table I. as the 

 consequent of the ratios, I avoided the confusion entailed by having two slightly 

 different mean differences for each range. There are, however, disadvantages, 

 which seemed to me to prevail in the case of the mean results for the 5 ranges 

 of Table II. In their case, accordingly, I made the small alterations required an 

 increment of less than \ per cent. to make the sum of the eleven ratios exactly 11. 



TABLE II. (Old Observations). Ratios of Differences Descending less Ascending 



Readings to Mean Difference. 



Before treating further the results shown in Tables I. and II. it is convenient 

 to notice some of the special experiments. 



Differences of Descending and Ascending Readings. Special Experiments. 



7. The first 24 special experiments were intended to serve for comparison of 

 the phenomena over different pressure ranges. They took place as follows, the 

 numbers showing the chronological order : 



